Extreme pressure lubricants



United States Patent 3,133,026 EXTREME PRESSURE LUBRICANTS William P. Scott, Ponca City, Okla, assignor to Continental Oil (Zompany, Ponce Qity, Okla, a corporation of Delaware No Drawing. Fiied Nov. 21, 1960, Ser. No. 79,444 4 (Claims. (Cl. 252-836) This invention relates to extreme pressure lubricants having improved properties and particularly lubricants adapted for heavy duty service. In one aspect, the invention relates to lubricating oils and in another aspect to lithium base greases.

The prior art discloses numerous additives which are employed to provide E.P. (extreme pressure) properties to lubricating oils and greases. For example, Langner, US. Patent No. 2,785,130, discloses extreme pressure lubricants comprising lubricating oils containing a lead soap, polyhydric alcohol, and extreme pressure agent selected from halogenated an sulfohalogenated organic compounds. It is taught in this patent that it is essential to provide an extreme pressure agent containing a portion of a halogenated or sulfo-halogenated organic compound; thus the patentee in this instance derives at extreme pressure properties through the combined use of lead, alcohol, active halogen, and in some instances active sulfur. The patentee further teaches that extreme pressure properties are reduced by use of the alcohol in the absence of active halogen.

In US. Patent No. 2,858,273, impartation of ER properties to calcium soap greases is provided by incorporating as additives a polyhydric alcohol, a metal organodithiocarbamate, and an alkanol amine. The patentee teaches that the alkanol amine is essential to his greases in order to provide good mechanical stability. He further teaches that only those alcohols containing 3 or 4 hydroxyl groups are operative in his compositions.

The applicant has found that certain specific greases and lubricating oils in general can be considerably improved in E.P. properties by the use of a particular combination of additives not disclosed by the prior art.

It is therefore an object of this invention to provide improved lithium soap greases having high E.P. properties.

It is another object of this invention to provide improved lithium IZ-hydroxy stearate greases having improved E.P. properties.

Still another object of this invention is to provide improved lithium soap greases containing small amounts of an aliphatic polyhydric alcohol and a metal organodithiocarbamate.

Yet another object of this invention is to provide improved lubricating oils having high E.P. properties and containing small amounts of an aliphatic polyhydric alcohol and a metal organodithiocarbamate.

The foregoing objects are realized broadly by providing lithium base lubricating greases comprising a mineral lubricating oil thickened with a lithium soap and having incorporated therein an aliphatic polyhydric alcohol and a metal organodithiocarbamate.

1n one aspect, the invention is directed to lubricating oils containing an aliphatic polyhydric alcohol and a metal organodithiocarbamate.

The mineral lubricating oils which are employed in the compositions of this invention can be derived from naphthene or paratfin base crude and can be either residual or distillate oil or a mixture thereof, depending on the particular grease or lubricant which is being prepared. For example, in an automotive gear lubricant, a blend of a residual oil with a distillate oil has been found particularly suitable in meeting the viscosity requirements for the various grades.

The lithium base lubricating greases, which are well 3,133,028 Patented May 12, 1964 known in the art, comprise a dispersion of a lithium soap in a mineral oil. Usually, a calculated amount of soap, between about 5 percent and about 25 percent or higher by weight, is dispersed in the mineral oil base followed by heating at an elevated temperature, for example, from about 350 to about 450 F. until the mixture thickens. Subsequently the hot grease is cooled to provide the final product. Mixing or milling can be provided as desired during any of the preparation steps. Various soaps or admixtures of soaps can be employed in the lithium base greases; however, preferably, the soaps are hydroxy fatty acid soaps of lithium. A particularly desirable grease is obtained through the employment of soaps derived from mixtures of a hydroxy fatty acid and a hydrogenated fatty material, for example, hydrogenated fish oil, castor oil, and the like. Further details concerning the latter greases and their method of preparation are set forth in US. Patent 2,475,589.

The polyhydric alcohol and metal organodithiocarbamate which are added to the lubricants of this invention can be incorporated in the grease at any stage in its preparation; however, preferably, these materials are added during the final steps of preparation. Any of the aliphatic polyhydric alcohols can be employed in the lubricating compositions, including alcohols containing 2,

in which R and R represent hydrogen or organic groupings similar or dissimilar in nature, and present in the molecule so that the sum R +R contains at least eight carbon atoms in alkyl groups, and the structural relationship indicated by the relative positions and linkages of the respective atoms in the formula. The organic groupings represented by R and R can be alkyl, aryl, alkylaryl, mixture of alkyl and aryl, cycloalkyl and heterocyclic groupings. These groupings can contain inorganic substituents, such as sulfur, oxygen, phosphorus and nitrogen, when special properties are sought. Particularly important to the proper functioning of these compounds is that they possess adequate solubility in the mineral base stock and for this reason it is generally required that the combined R and R groups, when wholly organic, contain a total of at least 8 carbon atoms in alkyl groups. Considerable improvement in this regard is effected by increasing the number of carbon atoms in alkyl groups to 10, 12, and 16, preferably.

The preferred dithiocarbamates are those in which the organo groups are alkyl groups and particularly the lead .dialkyldithiocarbamates, for example, lead diamyldithioferred as stated previously. Although very minor amounts of the polyhydric alcohol and the metal organodithiocarbamate provide improvement in ER properties, these materials are ordinarily employed within certain percentage ranges, namely, from about 0.1 to about 5.0 percent by weight of the alcohol based on the grease and preferably from about 0.3 to about 1 percent; and from about 0.4 to about percent of the metal organodithiocarbamate based on the grease and preferably from about 1.0 to about 4 percent. The compositions can also contain small amounts of the conventional additives which are incorporaterl for specific purposes, including anticorrosive agents, pour depressants, viscosity improvers, oxidation inhibitors, dyes, and the like.

The combination of the polyhydric alcohol and metal organodithiocarbamate is found to give substantial improvements in the extreme pressure properties of the lithium soap greases without a corresponding adverse effect on the mechanical stability of the greases and without limitation as to the type of polyhydric alcohol which is employed. This combination of additives also provides a similar effect in lubricating oils.

The following examples are presented in illustration of the invention:

Example 1 The following is given as an example of a base lubricant composition having extreme pressure properties:

Several blends were prepared in which various polyhydric alcohols were added to the above lubricating base. The following table shows the data obtained:

Weight Tirnken Test Polyhydrlc Alcohol Added Percent 0K Lord,

Addition Pounds None r Glycerin 0. 2 Glycerin 0.3 Ethylene glycol 0. 3 Polypropylene glycol 0.6 Polybutylene glycol 0. 6 Polybutylene glycol 4 0. 6 50 1 The Timken Test was run according to the direction given by the A.S.T.M. Committee D-2 (A.S.T.M. Bulletin No. 181, page 43, April 1952). Special Timken steel blocks N o. T 15349 and Timken cups No. T-48fi5l were used. Ten-minute rims are made at various load levels. These levels are increased until failure occurs which is indicated by obvious scoring of the test specimens. The maximum load without failure and the unit pressures existing at this maximum sale load are considered as the performance criteria.

2 Average molecular weight 1350-1100.

3 Average molecular weight 1,000.

4 Average molecular weight 1,500.

The above data illustrate the effectiveness of the combination of the polyhydr-ic alcohol with a metal organedithiocarbamate, glycerin being particularly effective as the alcohol.

Example 2 grease prepared by open kettle saponification of a mixture of hydrogenated castor oil and lZ-hydroxy stearic acid in a mineral lubricating oil. Its finished approximate composition was as follows:

Percent by weight Lithium soap 5.5 Mineral lubricating oil a 94.5

Weight Percent Dithio- Timken Test carbamate- OK"Load, Mineral Oil Pounds Mixture Weight Percent Addition Polyhydric Alcohol Added 7 o Ethylene Glycol"- Hexylene Glycol The above data illustrate the effectiveness of the com- 7 Example 3 The following data were obtained to illustrate the effect of glycerin on the mechanical stability of lithium greases similar to the base grease employed in Example 2:

BATCHES WITH GLYCERIN ADDED (10,000-POUND BATGHES) A.S.T.M. D 217-52'1 Penetration Grease Batch 'Ilmken 60 Stroke 10,000

Stroke 1 BATCHES WITHOUT GLYCERIN 3 10,000 strokes in five-hole Worker.

1. A lithium base lubricating grease consisting essentially of a mineral lubricating oil thickened with lithium fatty acid soap and containing between about 0.1 and.

about 5.0 percent glycerin and between about 0.4 and about 10.0 percent lead diamyldithiocarbamate.

2. A lithium base lubricating grease consisting essentially of a mineral lubricating oil thickened with between about 1 and about 25 percent of the lithium soap of a h droxy fatty acid and hydrogenated castor oil and containing from about 0.1 to about 5.0 percent glycerin and from about 0.4 to about 10.0 percent lead diamyldithiocarbamate.

3. The grease of claim 4 in which the acid is lZ-hydroxy stearic acid.

4. A lithium base lubricating grease consisting essentially of a mineral lubricating oil thickened with between about 1 and about 25 percent by Weight of the lithium soap of a hydroxy fatty acid and hydrogenated castor oil hydroxy fatty 5 6 and containing from about 0.3 to about 1.0 percent by 2,504,672 Farrington ct a1 Apr. 18, 1950 weight glycerin and from about 1.0 to about 4.0 per- 2,785,130 Langer Mar. 12, 1957 cent by weight lead diamyldithiocarbamate. 2,794,781 Diamond et a1 June 4, 1957 2,812,306 Liehe Nov. 5, 1957 References Citcfi in the file of this patent 5 2,358,273 Worth Oct. 28, 1958 UNITED STATES PATENTS OR PATENTS 2,201,258 B11886 y 21, 1940 50 ,1 7 Canada Sspt, 2 1954 2,400,106 Denison et a1 May 14, 1946 UNITED STATES PATENT OFFICE QETIFICATE OF CURRECTION Patent N00 3 lSS OQO May 12 1964 William P, Scott It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as o orrected below a Column l line 2O for 'an read "--and--- column lline 70 for the claim reference numeral "4' read-s 2 Signed and sealed this 10th day of November 1964::

(SEAL) Attest:

ERNEST W. SWIDER' EDWARD J. BRENNER Attesting Ufficer Commissioner of Patents 

1. A LITHIUM BASE LUBRICATING GREASE CONSISTING ESSENTIALLY OF A MINERAL LUBRICATIN OIL THICKENED WITH LITHIUM FATTY ACID SOAP AND CONTAINING BETWEEN ABOUT 0.1 AND ABOUT 5.0 PERCENT GLYCERIN AND BETWEEN ABOUT 0.4 AND ABOUT 10.0 PERCENT LEAD DIAMYLDITHIOCARBAMATE. 